Coupled inductor and the method to make the same

ABSTRACT

A coupled inductor has two coils made by film or a lithography processes, wherein a first coil is disposed on a top surface of a magnetic sheet and a second coil is disposed on the bottom surface of the magnetic sheet, for controlling the variations of the alignments of the two coils in a smaller range.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application Ser. No. 63/180,659 filed on Apr. 28, 2021, which is hereby incorporated by reference herein and made a part of the specification.

BACKGROUND OF THE INVENTION I. Field of the Invention

The present invention relates to a coupled inductor, and in particular, to a coupled inductor made by a film or a lithography process.

II. Description of Related Art

A conventional coupled inductor uses two coils made of discrete conductive wires, wherein each coil is wound on a corresponding pillar in a vertical direction. However, the variations of the position alignment of the two coils can vary in a larger range for the coupled inductors, which will affect the reliability and performance of the coupled inductors.

Furthermore, the conventional coupled inductor uses the first mold, as shown in FIG. 1A, and the second mold, as shown in FIG. 1B, wherein a first coil C1 is wound around a pillar P1 and a second coil C2 is wound around a pillar P2, so the deviation of the center of the column can be the sum of the first mold deviation and the second mold deviation plus the combined process deviation. In addition, each conventional coupled inductor is made separately, so the deviation of the center of the column is a Gaussian Distribution, which is a big variation range and not good for maintaining the reliability and performance of the products.

Furthermore, as shown in FIG. 1C and FIG. 1D, the gap between the upper coil C2 and the lower coil C1 can vary in a big range such as 0-76 um, which is also not good for maintaining the reliability and performance of the products.

Therefore, a better solution is needed to resolve the above-mentioned issues.

SUMMARY OF THE INVENTION

The present invention provides a coupled inductor having two coils, wherein each coil can have a single-coil structure produced through a lithography process, and through assembly, the axis of the first coil and the axis of the second coil can be accurately aligned to achieve a better and reliable coupling coefficient of the coupled inductor.

The present invention provides a method to make a plurality of coupled inductors in a single process, wherein the plurality of coupled inductors made of film processes can control the variations of the misalignment between the first coil and the second coil, wherein the standard deviation of K (coupling coefficient) value is decreased significantly for all of the finished products in batch production.

In one embodiment, a coupled inductor is disclosed, wherein the coupled inductor comprises: a first coil-structure, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil; a second coil-structure, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil; a magnetic sheet, wherein the first coil-structure is disposed over a top surface of the magnetic sheet, and the second coil-structure is disposed over a bottom surface of the magnetic sheet, wherein the first coil-structure and the second coil-structure are on two opposite sides of the magnetic sheet, wherein a vertical plane across the at least one first winding turn of the first coil-structure, a first hollow space of the at least one first winding turn of the first coil-structure, the at least one second winding turn of the second coil-structure, and a second hollow space of the at least one second winding turn of the second coil-structure, a horizontal distance between the axis of the first coil and the axis of the second coil is not greater than 1 um.

In one embodiment, a coupled inductor is disclosed, wherein the coupled inductor comprises: a first coil-structure, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a first bottom insulating layer with said first conductive layer being formed on first bottom insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil; and a second coil-structure, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a second bottom insulating layer with said second conductive layer being formed on second bottom insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil; and wherein the at least one first winding turn of the first coil-structure and the at least one second winding turn of the second coil-structure are stacked along a vertical direction with a vertical distance between the at least one first winding turn of the first coil and the at least one second winding turn of the second coil, wherein on a vertical plane across the at least one first winding turn of the first coil-structure, a first hollow space of the at least one first winding turn of the first coil-structure, the at least one second winding turn of the second coil-structure, and a second hollow space of the at least one second winding turn of the second coil-structure, a horizonal distance between a first middle point of a first horizontal line segment and a second middle point of a second horizontal line segment is not greater than 1 um, wherein the first horizontal line segment extends from a first innermost edge to a second innermost edge across the first hollow space of the at least one first winding turn of the first coil-structure; and wherein the second horizontal line segment extends from a third innermost edge to a fourth innermost edge across the second hollow space of the at least one second winding turn of the second coil-structure.

In one embodiment, each of the first coil-structure and the second coil-structure is formed by a corresponding lithography process, wherein the at least one first winding turn of the first coil and the at least one second winding turn of the second coil are formed by the same set of image patterns being used in the said corresponding lithography process.

In one embodiment, the first coil-structure is disposed over a top surface of a magnetic sheet, and the second coil-structure is disposed over the bottom surface of the magnetic sheet, wherein the first coil-structure and the second coil-structure are on two opposite sides of the magnetic sheet.

In one embodiment, the coupled inductor further comprises a first magnetic body and a second magnetic body, wherein the first magnetic body is disposed on the top surface of the magnetic sheet to encapsulate the at least one first winding turn of the first coil, and wherein the second magnetic body is disposed on the bottom surface of the magnetic sheet to encapsulate the at least one second winding turn of the second coil.

In one embodiment, the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the first bottom insulating layer, wherein the first bottom insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the first bottom insulating layer, wherein the first plurality of conductive layers are located between the first bottom insulating layer and a first top insulating layer of the first coil-structure, wherein the first bottom insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second top insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the first magnetic body comprises a first unitary magnetic body that encapsulates the at least one first winding turn of the first coil and extends into the first hollow space of the first coil.

In one embodiment, the second magnetic body comprises a second unitary magnetic body that encapsulates the at least one second winding turn of the second coil and extends into the second hollow space of the first coil.

In one embodiment, a third insulating layer is formed on a first conductive layer comprising the first winding turn being formed on the first insulating layer, wherein the third insulating layer encapsulates the first winding turn and extends into an unpatterned area of the first conductive layer.

In one embodiment, a fourth insulating layer is formed on a second conductive layer comprising the second winding turn being formed on the second insulating layer, wherein the fourth insulating layer encapsulates the second winding turn and extends into an unpatterned area of the second conductive layer.

In one embodiment, each of the at least one first conductive layer is formed by a film process.

In one embodiment, each of the at least one first conductive layer is formed by a thin film process.

In one embodiment, the first conductive layer is formed by a thick film process.

In one embodiment, the first magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, each of the first magnetic body and the magnetic sheet is formed by a first material.

In one embodiment, each of the first magnetic body and the second magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, the first magnetic body is formed by a first material, the magnetic sheet is formed by a second material, and the second magnetic body is formed by a third material, wherein the first material, the second material, and the third material are different from each other.

In one embodiment, a unitary magnetic body is disposed over the first coil and extends into a first hollow space of the first coil and a second hollow space of the second coil.

In one embodiment, a first electrode, a second electrode, a third electrode, and a fourth electrode are disposed on a bottom surface of a magnetic body comprising the first magnetic body and the second magnetic body.

In one embodiment, a coupled inductor is disclosed, wherein the coupled inductor comprises: a first coil-structure, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a first bottom insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil; and a second coil-structure, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a second bottom insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil; and wherein the at least one first winding turn of the first coil-structure and the at least one second winding turn of the second coil-structure are stacked along a vertical direction with a vertical distance between the at least one first winding turn of the first coil and the at least one second winding turn of the second coil, wherein the first coil-structure and the first coil-structure are formed according to a same set of imaging patterns such that the relative position of the axis of the first coil to the shape of the first coil is the same as the relative position of the axis of the at least one second winding turn of the second coil to the shape of the second coil.

To make the aforementioned and other features and advantages of the present invention more comprehensible, several embodiments accompanied by figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention, the drawings are briefly described as follows.

FIGS. 1A-1D each shows a partial view of a conventional coupled inductor;

FIG. 2A shows a view of a coupled inductor according to one embodiment of the present invention;

FIG. 2B shows a coil structure formed on a carrier according to one embodiment of the present invention;

FIGS. 2C-2D each shows a corresponding coil structure after the carrier is removed according to one embodiment of the present invention;

FIG. 2E shows a top view of a coupled inductor according to one embodiment of the present invention;

FIGS. 3A-3B each illustrate a method to form a coupled inductor according to one embodiment of the present invention;

FIG. 4A shows stacked sheets for forming a plurality of coupled inductors according to one embodiment of the present invention;

FIG. 4B shows a way to align the sheets for forming a plurality of coupled inductors according to one embodiment of the present invention;

FIG. 5 illustrate a method to form a coupled inductor according to one embodiment of the present invention;

FIG. 6 illustrates a curve to show the position alignment relative to the coupling coefficient and mutual inductance of the two coils of the coupled inductor; and

FIGS. 7A-7D each illustrates a section view of a coupled inductor according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The present invention discloses a coupled inductor, wherein the coupled inductor comprises: a first coil formed by a film process, wherein the first coil comprises at least one first winding turn; and a second coil formed by a film process, wherein the second coil comprises at least one second winding turn, wherein the position misalignments between the first coil and the second coil can be minimized through the film process.

There are many ways to form the structure of the coupled inductor of the present invention, which will be described hereafter.

FIG. 2A shows a view of a coupled inductor according to one embodiment of the present invention. As shown in FIG. 2A, the coupled inductor 100 comprises: a first coil-structure 101, comprising at least one first conductive layer 101 c, 101 d, wherein each conductive layer 101 c, 101 d is formed on a corresponding insulating layer 101 b, 101 e, wherein the at least one first conductive layer 101 c, 101 d comprises first conductive patterns for forming at least one first winding turn of a first coil; a second coil-structure 102 comprising at least one second conductive layer 102 c, 102 d wherein each conductive layer 102 c, 102 d is formed on a corresponding insulating layer 102 b, 102 e, wherein the at least one second conductive layer 102 c, 102 d comprises second conductive patterns for forming at least one second winding turn of a second coil; a magnetic sheet 103, wherein the first coil-structure 101 is disposed over a top surface of the magnetic sheet 103, and the second coil-structure 102 is disposed over a bottom surface of the magnetic sheet 103, wherein the first coil-structure 101 and the second coil-structure 102 are on two opposite sides of the magnetic sheet 103, wherein a straight line passes through a first hollow space 101 h of the at least one first winding turn of the first coil and a second hollow space 102 h of the at least one second winding turn of the second coil.

In one embodiment, an outer side surface of each of the at least one first conductive layer 101 c, 101 d is encapsulated by an insulating layer 101L.

In one embodiment, an outer side surface of each of the at least one second conductive layer 102 c, 102 d is encapsulated by an insulating layer 102L.

In one embodiment, an inner side surface of each of the at least one first conductive layer 101 c, 101 d is encapsulated by an insulating layer 101U.

In one embodiment, an inner side surface of each of the at least one second conductive layer 102 c, 102 d is encapsulated by an insulating layer 102U.

In one embodiment, a first electrode E1 and a second electrode E2 of the coupled inductor are electrically connected to the first coil, and a third electrode E3 and a fourth electrode E4 of the coupled inductor are electrically connected to the second coil, as shown in FIG. 2E.

In one embodiment, wherein a vertical line passes through the first hollow space 101 h of the at least one first winding turn of the first coil and the second hollow space 102 h of the at least one second winding turn of the second coil.

In one embodiment, the coupled inductor 100 comprises a first magnetic body 104, wherein the first magnetic body 104 is disposed on the top surface of the magnetic sheet 103 to encapsulate the at least one first winding turn of the first coil; and a second magnetic body 105, wherein the second magnetic body 105 is disposed on the bottom surface of the magnetic sheet 103 to encapsulate the at least one second winding turn of the second coil.

In one embodiment, a first electrode E1 and a second electrode E2 of the coupled inductor are electrically connected to the first coil, and a third electrode E3 and a fourth electrode E4 of the coupled inductor are electrically connected to the second coil, wherein the first electrode E1, the second electrode E2, the third electrode E3, and the fourth electrode E4 are disposed on a bottom surface of the second magnetic body 105, as shown in FIG. 3.

In one embodiment, a first electrode and a second electrode of the coupled inductor are electrically connected to the first coil, and a third electrode and a fourth electrode of the coupled inductor are electrically connected to the second coil, wherein the first electrode, the second electrode, the third electrode, and the fourth electrode are disposed on a top surface of the first magnetic body 104.

In one embodiment, the at least one first conductive layer 101 c, 101 d comprises a first plurality of conductive layers 101 c, 101 d, wherein each conductive layer 101 c, 101 d of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer 101 b, 101 d starting from a first bottom insulating layer 101 b, wherein the first bottom insulating layer 101 b is in contact with the top surface of the magnetic sheet. In one embodiment, the first bottom insulating layer 101 b is formed on a carrier first, and the first plurality of conductive layers 101 c, 101 d are formed over the first bottom insulating layer 101 b, and the carrier is removed after the first coil-structure 101 is formed.

In one embodiment, the at least one first conductive layer 101 c, 101 d comprises a first plurality of conductive layers 101 c, 101 d, wherein each conductive layer 101 c, 101 d of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer 101 b, 101 d starting from a first bottom insulating layer 101 b, wherein the first bottom insulating layer 101 b is in contact with the top surface of the magnetic sheet 103.

In one embodiment, the first bottom insulating layer 101 b is formed on a carrier first, and the first plurality of conductive layers 101 c, 101 d are formed over the first bottom insulating layer 101 b, and the carrier is removed after the first coil-structure 101 is formed.

In one embodiment, the first plurality of conductive layers are located between the first bottom insulating layer 101 b and a first top insulating layer 101 a, wherein the first bottom insulating layer 101 b is in contact with the top surface of the magnetic sheet 103.

In one embodiment, the at least one second conductive layer 201 c, 201 d comprises a second plurality of conductive layers 201 c, 201 d, wherein each conductive layer 201 c, 201 d of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer 201 b, 201 d starting from a second bottom insulating layer 201 b, wherein the second bottom insulating layer 201 b is in contact with the top surface of the magnetic sheet 103.

In one embodiment, the second bottom insulating layer 201 b is formed on a carrier first, and the second plurality of conductive layers 201 c, 201 d are formed over the second bottom insulating layer 201 b, and the carrier is removed after the second coil-structure 102 is formed.

In one embodiment, the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet 103.

In one embodiment, the first magnetic body 104 comprises a first unitary magnetic body that encapsulates the at least one first winding turn of the first coil and extends into the first hollow space of the first coil.

In one embodiment, the second magnetic body 105 comprises a second unitary magnetic body that encapsulates the at least one second winding turn of the second coil and extends into the second hollow space of the first coil.

In one embodiment, the first winding turn is formed on the first bottom insulating layer, wherein a corresponding insulating layer is formed on a first conductive layer comprising the first winding turn, wherein said corresponding insulating layer encapsulates the first winding turn and extends into an unpatterned area of the first conductive layer.

In one embodiment, the second winding turn is formed on the second bottom insulating layer, wherein a corresponding insulating layer is formed on a second conductive layer comprising the second winding turn, wherein said corresponding insulating layer encapsulates the second winding turn and extends into an unpatterned area of the second conductive layer.

In one embodiment, the first coil is formed by a first plurality of conductive layers by a film process, wherein the first winding turn of the first coil is formed on the first insulating layer, wherein a third insulating layer is formed on the first winding turn, and a third winding turn is formed on the third insulating layer, wherein a fifth insulating layer is formed on a top surface of the first coil, wherein the first insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the first insulating layer can be formed on a first carrier 200, as shown in FIG. 2B, and the first carrier 200 is removed after the first coil-structure 101 is formed, as shown in FIG. 2C, wherein a hollow space 101 h of the first coil is formed.

In one embodiment, the second coil is formed by a second plurality of conductive layers by a film process, wherein the second winding turn is formed on the second insulating layer, wherein a fourth insulating layer is formed on the second winding turn, and a fourth winding turn is formed on the fourth insulating layer, wherein a sixth insulating layer is formed on a top surface of the second coil, wherein the second insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the second insulating layer can be formed on a second carrier; and the second carrier is removed after the second coil-structure 102 is formed, as shown in FIG. 2D, wherein a hollow space 102 h of the second coil is formed.

In one embodiment, a first electrode E1 and a second electrode E2 of the coupled inductor are electrically connected to the first coil, and a third electrode E3 and a fourth electrode E4 of the coupled inductor are electrically connected to the second coil, wherein the first electrode E1, the second electrode E2, the third electrode E3, and the fourth electrode E4 are disposed on a bottom surface of the second magnetic body 105, as shown in FIG. 2E.

In one embodiment, each of the at least one first conductive layer is formed by a thin film process.

In one embodiment, each of the first conductive layer is formed by a thick film process.

In one embodiment, the first magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, each of the first magnetic body and the magnetic sheet is formed by a first material.

In one embodiment, each of the first magnetic body and the second magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, the first magnetic body is formed by a first material, the magnetic sheet is formed by a second material, and the second magnetic body is formed by a third material, wherein the first material, the second material, and the third material are different from each other.

In one embodiment, as shown in FIG. 3A, a method to form a coupled inductor is disclosed, wherein said method comprises: step 201: forming a first coil-structure on a carrier, wherein the first coil-structure comprises at least one first conductive layer with each conductive layer being formed on a corresponding insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil; step 202: forming a second coil-structure on the carrier, wherein the second coil-structure comprises at least one second conductive layer with each conductive layer being formed on a corresponding insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil; step 203: removing the carrier to obtain the first coil-structure comprising the first insulating layer and the first coil formed on the first insulating layer and the second coil-structure comprising the second insulating layer and the second coil formed on the second insulating layer; step 204: disposing the first coil-structure on a top surface of the magnetic sheet, and disposing the second coil-structure on a bottom surface of the magnetic sheet.

In one embodiment, a vertical line passes through a first hollow space of the at least one first winding turn of the first coil and a second hollow space of the at least one second winding turn of the second coil.

In one embodiment, each of the at least one first conductive layer is formed by a film process.

In one embodiment, each of the at least one first conductive layer is a metal layer formed by a thin film process.

In one embodiment, the first conductive layer is formed by a thick film process.

In one embodiment, the method further comprises disposing a first magnetic body on the top surface of the magnetic sheet to encapsulate the at least one first winding turn of the first coil and extend into the first hollow space of the first coil.

In one embodiment, the method further comprises disposing a second magnetic body on the bottom surface of the magnetic sheet to encapsulate the at least one second winding turn of the second coil and extend into the first second space of the second coil.

In one embodiment, the first magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, each of the first magnetic body and the magnetic sheet is formed by a first material.

In one embodiment, each of the first magnetic body and the second magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, the first magnetic body is formed by a first material, the magnetic sheet is formed by a second material, and the second magnetic body is formed by a third material, wherein the first material, the second material, and the third material are different from each other.

In one embodiment, the first insulating layer is in contact with the top surface of the magnetic sheet, and the second insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the first coil is formed by a first plurality of conductive layers, wherein the first winding turn is formed on a first insulating layer disposed on the carrier, wherein a third insulating layer is formed on the first winding turn, wherein the first insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the second coil is formed by a second plurality of conductive layers, wherein the second winding turn is formed on a second insulating layer disposed on the carrier, wherein a fourth insulating layer is formed on the first winding turn, wherein the second insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the first coil is formed by a first plurality of conductive layers, wherein the first winding turn is formed on the first insulating layer, wherein a third insulating layer is formed on the first winding turn, and a third winding turn is formed on the third insulating layer, wherein a fifth insulating layer is formed on a top surface of the first coil, wherein the first insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, as shown in FIG. 3B, a method for forming a plurality of coupled inductors is disclosed, wherein the method comprises: step 301: forming a first insulating layer on a first carrier, and forming at least one first conductive layer over the first insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming a plurality of first coils; 302: removing the first carrier to obtain a first sheet comprising the first insulating layer and the plurality of first coils; step 303: forming a second insulating layer on a second carrier and forming at least one second conductive layer over the second insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming a plurality of second coils; step 304: removing the second carrier to obtain a second comprising the second insulating layer and the plurality of second coils; step 305: disposing the first sheet on a top surface of a third sheet comprising a magnetic material and disposing the second sheet on a bottom surface of the third sheet.

As shown in FIG. 4A, the first sheet 401 is disposed on the top surface of the third sheet 403, and the second sheet 402 is disposed on the bottom surface of the third sheet.

In one embodiment, the method comprises disposing a fourth sheet 404 comprising a magnetic material on the top surface of the first sheet 401. As shown in FIG. 4A, the fourth sheet 404 is disposed on the top surface of the first sheet 401.

In one embodiment, the method comprises disposing a fifth sheet 405 comprising a magnetic material on the bottom surface of the second sheet 402. As shown in FIG. 4A, the fifth sheet 405 is disposed on the bottom surface of the second sheet 402.

In one embodiment, as shown in FIG. 4A, the sheets 401, 402, 403, 404, 405 can be disposed in a mode 406 for alignment of the sheets 401, 402 comprising coils. The alignment of the coils can be side alignment, pin alignment, or tenon alignment. Different from the prior art, batch alignment accuracy is a fixed value, which can reduce the gap variations for all finished products in batch production.

In one embodiment, the sheets 401, 402 comprising coils can be aligned by the optical alignment such as CCD, laser, image, etc. As shown in FIG. 4B, each of the sheets 401, 402 has some holes 401 h, 402 h for passing the lights from CCD 500 for alignment of the sheets 401, 402 comprising coils. Different from the prior art, batch alignment accuracy is a fixed value, which can reduce the gap variations for all finished products.

In one embodiment, the first insulating layer is in contact with the top surface of the third sheet, and the second insulating layer is in contact with the bottom surface of the third sheet.

In one embodiment, the first coil is formed by a first plurality of conductive layers, wherein the first winding turn is formed on a first insulating layer disposed on the carrier, wherein a third insulating layer is formed on the first winding turn, wherein the first insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the second coil is formed by a second plurality of conductive layers, wherein the second winding turn is formed on a second insulating layer disposed on the carrier, wherein a fourth insulating layer is formed on the first winding turn, wherein the second insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, as shown in FIG. 5, a method for forming a plurality of coupled inductors is disclosed, wherein the method comprises: step 401: forming a first sheet and a second sheet by film processes, wherein each of the first sheet and the second sheet comprises at least one conductive layer with each conductive layer formed on a corresponding insulating layer, wherein the at least one conductive layer comprises conductive patterns for forming a plurality of coils; 402: disposing the first sheet on a top surface of a third sheet comprising a magnetic material and disposing the second sheet on a bottom surface of the third sheet, wherein a fourth sheet is disposed on the top surface of the first sheet 401 and a fifth sheet 405 is disposed on the bottom surface of the second sheet 402, wherein the stacked sheets are hot pressed to form a magnetic body with coils of coupled inductors inside the magnetic body; step 403: cutting the magnetic body into a plurality of pieces with each piece comprising a corresponding portion of the magnetic body and two corresponding coils of a coupled inductor inside the corresponding portion of the magnetic body; step 404: spraying paint on the magnetic body of the coupled inductor; step 405: peeling paint from the magnetic body of the coupled inductor; step 406: electroplating Cu paint on the magnetic body; step 407: spraying paint; step 408: peeling paint; step 409: electroplating Cu/Ni/Sn; step 410: finished product of the coupled inductor.

FIG. 6 illustrates a curve to show the distance between two coils relative to the coupling coefficient K and the mutual inductance L11 of the two different coils of the coupled inductor, wherein the distance between the first coil and the second coil can cause the coupling coefficient K and the mutual inductance L11 varies. Therefore, the alignment of the two coils, having a single coil structure, of the coupled inductors, can control the variations of the coupling coefficient and the mutual inductance of the two different coils of the coupled inductor, thereby improving the reliability of the coupled inductors.

In one embodiment, as shown in FIG. 7A, a coupled inductor is disclosed, wherein the coupled inductor comprises: a first coil-structure 101, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a first bottom insulating layer 101 b with said first conductive layer being formed on and in contact with the first bottom insulating layer 101 b, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil, said first winding turn being an innermost winding turn of the first coil; and a second coil-structure 102, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer starting from a second bottom insulating layer 102 b with said second conductive layer being formed on and in contact with the second bottom insulating layer 102 b, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil, said second winding turn being an innermost winding turn of the second coil; and wherein the at least one first winding turn of the first coil-structure and the at least one second winding turn of the second coil-structure are stacked along a vertical direction with a vertical distance G between the at least one first winding turn of the first coil and the at least one second winding turn of the second coil.

As shown in FIG. 7A, on a first vertical plane 700 across the at least one first winding turn of the first coil-structure 101, a first hollow space 101 h of the at least one first winding turn of the first coil-structure 101, the at least one second winding turn of the second coil-structure 102, and a second hollow space 102 h of the at least one second winding turn of the second coil-structure 102, a horizontal distance d between a first middle point UM1 of a first horizontal line segment L1 and a second middle point LM1 of a second horizontal line segment L2 is not greater than 1 um, wherein the first horizontal line segment L1 extends from a first edge US1 to a second edge US2 of the first winding turn of the first coil across the first hollow space 101 h of the first coil; and wherein the second horizontal line segment L2 extends from a third edge LS1 to a fourth edge LS2 across the second hollow space 102 h of the second coil. The horizontal distance d is measured between the vertical line VU1 passing the first middle point UM1 and the vertical line VL1 passing the second middle point LM1.

In one embodiment, as shown in FIG. 7B, the horizontal distance d is zero, wherein the vertical line V1 is passing the first middle point UM1 and the second middle point LM1.

In one embodiment, each of the first coil-structure 101 and the second coil-structure 102 is formed by a corresponding lithography process, wherein the at least one first winding turn of the first coil and the at least one second winding turn of the second coil are formed by the same set of image patterns being used in the said corresponding lithography process.

In one embodiment, the first coil-structure 101 is disposed over a top surface of a magnetic sheet 103, and the second coil-structure 102 is disposed over a bottom surface of the magnetic sheet 103, wherein the first coil-structure 101 and the second coil-structure 102 are on two opposite sides of the magnetic sheet.

In one embodiment, as shown in FIG. 2A, the coupled inductor further comprises a first magnetic body and a second magnetic body, wherein the first magnetic body is disposed on the top surface of the magnetic sheet to encapsulate the at least one first winding turn of the first coil, and wherein the second magnetic body is disposed on the bottom surface of the magnetic sheet to encapsulate the at least one second winding turn of the second coil.

In one embodiment, as shown in FIG. 7A, the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the first bottom insulating layer, wherein the first bottom insulating layer is in contact with the top surface of the magnetic sheet.

In one embodiment, the first winding turn of the first coil in formed on and in contact with the first bottom insulating layer.

In one embodiment, as shown in FIG. 7C, the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the first bottom insulating layer, wherein the first plurality of conductive layers are located between the first bottom insulating layer and a first top insulating layer of the first coil-structure, wherein the first bottom insulating layer is in contact with the top surface of the magnetic sheet. The horizontal distance d is measured between the vertical line VU1 passing the first middle point UM1 and the vertical line VL1 passing the second middle point LM1.

In one embodiment, as shown in FIG. 7C, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, the second winding turn of the first coil in formed on and in contact with the second bottom insulating layer.

In one embodiment, as shown in FIG. 7A, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second top insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, as shown in FIG. 7C, the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet.

In one embodiment, as shown in FIG. 7D, the horizontal distance d is zero, wherein the vertical line V1 is passing the first middle point UM1 and the second middle point LM1.

In one embodiment, the first magnetic body comprises a first unitary magnetic body that encapsulates the at least one first winding turn of the first coil and extends into the first hollow space of the first coil.

In one embodiment, the second magnetic body comprises a second unitary magnetic body that encapsulates the at least one second winding turn of the second coil and extends into the second hollow space of the first coil.

In one embodiment, a third insulating layer is formed on a first conductive layer comprising the first winding turn being formed on the first insulating layer, wherein the third insulating layer encapsulates the first winding turn and extends into an unpatterned area of the first conductive layer.

In one embodiment, a fourth insulating layer is formed on a second conductive layer comprising the second winding turn being form on the second insulating layer, wherein the fourth insulating layer encapsulates the second winding turn and extends into an unpatterned area of the second conductive layer.

In one embodiment, each of the at least one first conductive layer is formed by a film process.

In one embodiment, each of the at least one first conductive layer is formed by a thin film process.

In one embodiment, the first conductive layer is formed by a thick film process.

In one embodiment, the first magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, each of the first magnetic body and the magnetic sheet is formed by a first material.

In one embodiment, each of the first magnetic body and the second magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.

In one embodiment, the first magnetic body is formed by a first material, the magnetic sheet is formed by a second material, and the second magnetic body is formed by a third material, wherein the first material, the second material, and the third material are different from each other.

In one embodiment, a unitary magnetic body is disposed over the first coil and extends into a first hollow space of the first coil and a second hollow space of the second coil.

In one embodiment, a first electrode, a second electrode, a third electrode, and a fourth electrode are disposed on a bottom surface of a magnetic body comprising the first magnetic body and the second magnetic body.

In one embodiment, on a second vertical plane across the at least one first winding turn of the first coil-structure, a first hollow space of the at least one first winding turn of the first coil-structure, the at least one second winding turn of the second coil-structure, and a second hollow space of the at least one second winding turn of the second coil-structure, a second horizontal distance between a third middle point of a third horizontal line segment and a fourth middle point of a fourth horizontal line segment is not greater than 1 um, wherein the third horizontal line segment extends from a fifth innermost edge to a sixth innermost edge across the first hollow space of the at least one first winding turn of the first coil-structure; and wherein the fourth horizontal line segment extends from a seventh innermost edge to an eighth innermost edge across the second hollow space of the at least one second winding turn of the second coil-structure, wherein the second vertical plane is perpendicular to the first vertical plane.

The present invention can achieve the following advantages: a single-coil structure can be produced through a lithography process, through assembly, the first coil and the second coil having the same coil structure can be accurately aligned on the same axis to achieve a better and more reliable coupling coefficient of coupled inductors in batch production; the standard deviation of the gap between the upper coil and the lower coil in finished coupled inductors can be reduced from 2.6 to 0.6 through structural design optimization, especially using the flatness of the bottom insulating layer of the upper coil structure and the flatness of the bottom insulating layer of the lower coil structure to form the gap between the upper coil and lower coil of the coupled inductor, which can improve product reliability and performance. In addition, the present invention can improve product quality and yield of the coupled inductors, wherein the standard deviation of the K (coupling coefficient) value is decreased significantly to 0.017, by using the flatness of the bottom insulating layer of the upper coil structure and the flatness of the bottom insulating layer of the lower coil structure.

Although the present invention has been described with reference to the above embodiments, it will be apparent to one of ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above-detailed descriptions. 

What is claimed is:
 1. A coupled inductor, comprising: a first coil-structure, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil, said first winding turn being an innermost winding turn of the first coil; and a second coil-structure, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil, said second winding turn being an innermost winding turn of the second coil; and wherein on a first vertical plane across the at least one first winding turn of the first coil-structure, a first hollow space of the at least one first winding turn of the first coil-structure, the at least one second winding turn of the second coil-structure, and a second hollow space of the at least one second winding turn of the second coil-structure, a first horizontal distance between a first middle point of a first horizontal line segment and a second middle point of a second horizontal line segment is not greater than 1 um, wherein the first horizontal line segment extends from a first edge to a second edge of said first winding turn of the first coil across said first hollow space of the at least one first winding turn of the first coil-structure, and the second horizontal line segment extends from a third edge to a fourth edge of said second winding turn of the second coil across said second hollow space of the at least one second winding turn of the second coil-structure.
 2. The coupled inductor according to claim 1, wherein the first coil-structure is disposed over a top surface of a magnetic sheet, and the second coil-structure is disposed over a bottom surface of the magnetic sheet, wherein the first coil-structure and the second coil-structure are on two opposite sides of the magnetic sheet.
 3. The coupled inductor according to claim 1, wherein on a second vertical plane across the at least one first winding turn of the first coil-structure, a first hollow space of the at least one first winding turn of the first coil-structure, the at least one second winding turn of the second coil-structure, and a second hollow space of the at least one second winding turn of the second coil-structure, a second horizontal distance between a third middle point of a third horizontal line segment and a fourth middle point of a fourth horizontal line segment is not greater than 1 um, wherein the third horizontal line segment extends from a fifth edge to a sixth edge of said first winding turn of the first coil across said first hollow space of the at least one first winding turn of the first coil-structure, and the fourth horizontal line segment extends from a seventh edge to an eighth edge of said second winding turn of the second coil across said second hollow space of the at least one second winding turn of the second coil-structure, wherein the second vertical plane is perpendicular to the first vertical plane.
 4. The coupled inductor according to claim 2, wherein the coupled inductor further comprises a first magnetic body and a second magnetic body, wherein the first magnetic body is disposed on the top surface of the magnetic sheet to encapsulate the at least one first winding turn of the first coil, and wherein the second magnetic body is disposed on the bottom surface of the magnetic sheet to encapsulate the at least one second winding turn of the second coil.
 5. The coupled inductor according to claim 2, wherein the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from a first bottom insulating layer, wherein the first winding turn of the first coil in formed on and in contact with the first bottom insulating layer, and the first bottom insulating layer is in contact with the top surface of the magnetic sheet.
 6. The coupled inductor according to claim 2, wherein the at least one first conductive layer comprises a first plurality of conductive layers, wherein each conductive layer of the first plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from a first bottom insulating layer, wherein the first plurality of conductive layers are located between the first bottom insulating layer and a first top insulating layer of the first coil-structure, wherein the first winding turn of the first coil in formed on and in contact with the first bottom insulating layer, and the first bottom insulating layer is in contact with the top surface of the magnetic sheet.
 7. The coupled inductor according to claim 5, wherein the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from a second bottom insulating layer, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet, wherein said first winding turn of the first coil in formed on and in contact with the first bottom insulating layer, and said second winding turn of the second coil in formed on and in contact with the second bottom insulating layer.
 8. The coupled inductor according to claim 5, wherein the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from a second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second top insulating layer is in contact with the bottom surface of the magnetic sheet, wherein said first winding turn of the first coil in formed on and in contact with the first bottom insulating layer, and said second winding turn of the second coil in formed on and in contact with the second bottom insulating layer.
 9. The coupled inductor according to claim 5, wherein the at least one second conductive layer comprises a second plurality of conductive layers, wherein each conductive layer of the second plurality of conductive layers is formed sequentially on a corresponding insulating layer starting from the second bottom insulating layer, wherein the second plurality of conductive layers are located between the second bottom insulating layer and a second top insulating layer of the second coil-structure, wherein the second bottom insulating layer is in contact with the bottom surface of the magnetic sheet, wherein said first winding turn of the first coil in formed on and in contact with the first bottom insulating layer, and said second winding turn of the second coil in formed on and in contact with the second bottom insulating layer.
 10. The coupled inductor according to claim 4, wherein the first magnetic body comprises a first unitary magnetic body that encapsulates the at least one first winding turn of the first coil and extends into the first hollow space of the first coil.
 11. The coupled inductor according to claim 10, wherein the second magnetic body comprises a second unitary magnetic body that encapsulates the at least one second winding turn of the second coil and extends into the second hollow space of the first coil.
 12. The coupled inductor according to claim 1, wherein a third insulating layer is formed on a first conductive layer comprising the first winding turn being formed on the first insulating layer, wherein the third insulating layer encapsulates the first winding turn and extends into an unpatterned area of the first conductive layer.
 13. The coupled inductor according to claim 12, wherein a fourth insulating layer is formed on a second conductive layer comprising the second winding turn being formed on the second insulating layer, wherein the fourth insulating layer encapsulates the second winding turn and extends into an unpatterned area of the second conductive layer.
 14. The coupled inductor according to claim 1, wherein each of the at least one first conductive layer is formed by a film process.
 15. The coupled inductor according to claim 4, wherein the first magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.
 16. The coupled inductor according to claim 4, wherein each of the first magnetic body and the second magnetic body is formed by a first material, and the magnetic sheet is formed by a second material that is different from the first material.
 17. The coupled inductor according to claim 4, wherein the first magnetic body is formed by a first material, the magnetic sheet is formed by a second material, and the second magnetic body is formed by a third material, wherein the first material, the second material, and the third material are different from each other.
 18. A coupled inductor, comprising: a first coil-structure, comprising at least one first conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one first conductive layer comprises first conductive patterns for forming at least one first winding turn of a first coil; a second coil-structure, comprising at least one second conductive layer, wherein each conductive layer is formed on a corresponding insulating layer, wherein the at least one second conductive layer comprises second conductive patterns for forming at least one second winding turn of a second coil; and wherein the at least one first winding turn of the first coil-structure and the at least one second winding turn of the second coil-structure are stacked along a vertical direction with a vertical distance between the at least one first winding turn of the first coil and the at least one second winding turn of the second coil, wherein the first coil-structure and the second coil-structure are formed according to a same set of imaging patterns, wherein the relative position of the axis of the first coil to the shape of the first coil is the same as the relative position of the axis of the second coil to the shape of the second coil.
 19. The coupled inductor according to claim 18, wherein the first coil-structure is disposed over a top surface of the magnetic sheet, and the second coil-structure is disposed over a bottom surface of the magnetic sheet, wherein the first coil-structure and the second coil-structure are on two opposite sides of the magnetic sheet.
 20. The coupled inductor according to claim 18, wherein the coupled inductor further comprises a first magnetic body and a second magnetic body, wherein the first magnetic body is disposed on the top surface of the magnetic sheet to encapsulate the at least one first winding turn of the first coil, and wherein the second magnetic body is disposed on the bottom surface of the magnetic sheet to encapsulate the at least one second winding turn of the second coil. 